The present invention relates to gravity filters, and particularly to gravity filters having multiple filter cells. More particularly, the present invention relates to gravity filters having multiple filter cells incorporating inlet flow splitting.
Conventional gravity filters typically employ multiple filter cells to allow cleaning of one filter cell while the other cells continue to operate. In a multi-cell arrangement, the total flow of influent to be filtered is typically split equally among the active cells. To facilitate this, the influent is pumped to an elevation well above the maximum influent level of the filter cells. The influent flows into a distribution box disposed above the filter cells. Weirs within the distribution box divide the distribution box into a plurality of distribution cells. Generally, the number of distribution cells is equal to the number of filter cells. Influent flows over the weirs to equally divide the flows between the distribution cells. The influent then flows out of each distribution cell and into the associated filter cell through a separate pipe or channel. Closing a valve in the pipe prevents flow of influent to a filter cell allowing a backwash cycle or maintenance to the cell.
As shown in FIG. 5, dividing the flow in a conventional filter system 10 requires that the influent be pumped to a level substantially higher than the filter cell maximum influent level 11 and then allowing the influent to flow past a weir 12 and into one of a plurality of pipes 15. The flow in the distribution box 20 is split at the weirs 12 before it enters each of the pipes 15. The head loss 17 is a measure of the difference between the maximum influent level in the distribution box 20 and the maximum level in the filter cell 11. To save on pumping costs, it is desirable to reduce the flow losses that accumulate in the flow splitting process.
Thus, according to the present invention a filter provides a plurality of filter cells, each filter cell including a bottom surface and at least one side surface and defining a maximum influent level. The filter also includes a distribution box including a base and at least one wall, the base and wall at least partially defining a distribution region therein. The filter further comprises a plurality of drop pipes, each pipe having a first end and a second end, the first end of each pipe extending into the distribution region, the first end defining a weir at a weir height. The second end of the pipe extends out of the distribution box and is in fluid communication with one of the plurality of filter cells.
The invention further provides a method of splitting a flow of influent between a plurality of filter cells. The method uses a distribution box and a plurality of drop pipes. The method comprises the steps of disposing a first end of each drop pipe within the distribution box. The method further includes positioning the first ends of each drop pipe at a weir height such that the first ends of the drop pipes define a plurality of weirs within the distribution box. The method further comprises disposing a second end of the pipe in fluid communication with one of the plurality of filter cells. The method additionally includes directing the flow of influent to the distribution box, and simultaneously splitting the flow and distributing the flow by passing a substantially equal portion of flow over each of the weirs, and passing the flow through the plurality of drop pipes to the filter cells.
In preferred embodiments, the distribution box is supported to provide a maximum influent level within the box that is between one inch and twenty-five inches above the maximum influent level within the filter cells. In addition, a plurality of baffles attach to the walls of the distribution box to define distribution cells. Each of the drop pipes extends into one of the distribution cells to define a continuous weir. An adjusting member coupled to the first end of each drop pipe allows the elevation of the weir to be positioned as desired. A valve, comprising a closure plate and actuator, is disposed above each pipe to close the pipe when the actuator moves the plate into the closed position.
Additional features and advantages will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.